The invention relates to quick attachment devices adapted to ensure that a piece of equipment is reliably and accurately retained on a person wearing it, while enabling such person to lock and unlock the device easily. It finds a particularly important application in the field of attaching respiratory masks used by crew during high altitude flights.
In this application the mask must remain in place even under exceptional circumstances, (for example, high speed ejection), and moreover the device must not be knocked out of shape as a result of handling or impacts causing jamming or breakage. In addition the device must be easy to unlock, even with one hand, possibly wearing a glove.
Quick attachment devices intended to meet this demand are known of the type comprising a receiver member attached to the helmet and a bayonet member borne by a mask strap and cooperating via locking means which can be retracted by pulling on a control plate borne by the bayonet-member and being able to slide thereon from an abutment position into which it is resiliently urged.
In such prior art devices, a representative example of which is given in U.S. Pat. No. 3,035,573, the locking means comprise in the receiver member a rack enabling the position of the mask to be adjusted, the bayonet member having movable locking fingers which are biased by springs into a position of engagement with the rack, and can be retracted by operating the control plate.
The method, which at first glance seems attractive, since it makes the fixed member carry the position-adjusting means and therefore simplifies the design of the control plate, has in fact appreciable disadvantages. Since the moveable piece comprises three elements disposed side by side, the control plate, the locking fingers and the bayonet member, the latter must be formed by a thin blade to avoid making the assembly too thick. There is a risk that the thin blade may get twisted or even broken by forces exerted accidentally.
It is an object of the invention to supply a rapid attachment device which satisfies practical demands more satisfactorily than the prior art devices, more particularly in that it is of reduced weight, occupies only a small amount of space, and at the same time has increased resistance to the bayonet member being torn off.
To this end the invention provides more particularly a device of the type hereinbefore defined whose bayonet member is formed by a solid blade provided with a rack engaging with retractable locking fingers borne by the receiver member, and the control plate comprises notches which have the same pitch as those of the rack and whose profile is such that they displace the resilient fingers out of the rack when the control plate is pulled, in the direction corresponding to the withdrawal of the bayonet member, from the abutment position into which it is resiliently urged.
The invention will be more clearly understood from the following description of a non-limitative exemplary embodiment thereof.